Nyctibuis_griseus
This bird was found in the local town of Ituzaingo close to the river. They are visible during the day but blend in so well with branches of the tree that they are very difficult to find. The easiest time to identify them is at dusk when they have a very distinctive call.
Their length is around 35cm and the colour resembles tree bark which is why they are so well camoflaged. The tail is long and barred and the head a little like a Nightjar with a short and wide bill and orange eyes. They are from the family Nyctibidae of which there are 2 species in Argentina.
It is a nocturnal insectivore and reasonably common in the Ibera area.